Scientia Sinica

92 SCIENTIA SINICA Vol, V

electrophoretic behaviour of carp nucleotropomyosin; and quite recently Snellman and Tcnow!! reported the isolation from human and bovine uteri the socalled contractile “actotropomyosin”, the existence of which we disputed in an earlier paper. In this laboratory we have modified Bailey’s classical procedures and evolved a general method" for the isolation of tropomyosins from the skeletal, the cardiac and the smooth muscles of cow, pig, rabbit, rat, pigeon, duck, snake, toad, carp, shell carp and crab. We have also demonstrated that during the later stages of embryonic development and throughout the course of pregnancy the tropomyosin content of the respective bovine foetus and uterus appeared to remain constant. In those investigations, the differences in crystalline form, in ribonucleic acid content, and in viscosity behaviour suggested to us that there might be significant differences in the macromolecular structure of tropomyosins from different sources. This contention has now been confirmed experimentally. The aim of this paper is to present the results with regard to the size, shape, polymerizability, solubility and electrophoretic mobility of tropomyosins from different types of muscle. The isolation and crystallization of tropomyosins from sepia mantle, from the body muscle of prawn and from the foot and adductor muscles of bivalves will also be described. The determination of the yet deeper differences in chemical structure will be the substance for a later communication.

II]. ExpermmENTAL

I. Biological material.

We selected pig heart, duck gizzard, sepia mantle and the body muscle of prawn as our experimental material for subsequent physicochemical studies. Cold-preserved sepia (Sepia esculenta) and prawn (Penaeus orientalis) were obtained from a fishmonger, and fresh pig heart and duck gizzard from the local slaughter-house; they were kept in crushed-ice during transport. Of these we chose the pig heart and the duck gizzard to represent respectively cardiac and smooth muscles of vertebrates, and the prawn and the sepia mantle to be examples of striated and smooth muscles of invertebrates. The bivalves employed were Anodonta pacifica Heude and Cristaria plicata Leach.

2. Extraction, purification and crystallization of tropomyosin.

Pig heart, sepia mantle and bivalve foot tropomyosins were prepared according to Bailey’s classical procedures’! *!. The method for the preparation of duck gizzard tropomyosin was described in a previous paper of ours).

The texture of the prawn muscle and the solubility behaviour of the extracted tropomyosin differ considerably from other muscle systems, thus necessitating slight alterations of the usual procedures. The body muscle of the prawn was cut into large lumps and immersed in 3 volumes of ethanol